Each of the following patent documents discloses a method for forming a semiconductor element on a semiconductor wafer.
Patent Document 1: JP-A-1990-30132
Patent Document 2: JP-A-2005-217320
Patent Document 3: JP-A-2005-123263
Patent Document 4: JP-A-1995-45560
Patent Document 5: JP-A-1994-45315
Patent Document 6: JP-A-2005-72538
Patent Document 7: International Publication No. 2002-103808
A conventional method for forming an element having a minute structure with a movable portion, such as an acceleration sensor, is to stack a plurality of films having different materials and thicknesses on a semiconductor wafer and process the films. The present inventor(s) found out that a crack may occur in the films due to stresses present in the films when the films are stacked. If the crack propagates into the semiconductor wafer, a film on or above which the element is to be formed will be damaged, or the element itself will be damaged.
In recent years, after elements such as acceleration sensors are formed on semiconductor wafers, business transactions involving sales of the wafers have been performed without dicing the wafer. Therefore, it is desirable to take measures to prevent such a crack in a process for manufacturing a semiconductor wafer (hereinafter also referred to as an element wafer) having an element formed thereon.